Medications such as insulin must presently be administered by subcutaneous injection. Such injections are painful, resulting in refusal among diabetics to administer the required doses at the appropriate times. Additionally, the absorption of the insulin is affected by the site of the injection, the temperature of the tissue, the vascularity of the tissue, and the activity of the underlying muscle. Failure to properly deliver the appropriate insulin doses to properly regulate blood sugar results in development of various complications of diabetes, such as blindness.
Metered dose spray devices are presently used to administer many different medications to the mouth and lungs, for example, asthma medication and nitroglycerin for treatment of heart disease. A typical metered dose spray device includes a can for containing a solution or suspension of medication, a metering valve, and an actuator. The can will contain the medication to be dispensed, possibly a solvent for the medication, and a propellant. The propellant is a substance having a low boiling point and high vapor pressure, so that as liquid is dispensed from the container the propellant evaporates, maintaining a constant pressure within the can. Actuation of the metering valve causes the metering chamber within the valve to close with respect to the can, and open with respect to the mouthpiece. Propellants within the metering chamber will evaporate due to the sudden decrease in pressure when the valve is actuated, propelling the medication into the user's mouth.
Presently available metered dose spray devices are not suitable for dispensing medication that is to be absorbed through the buccal cavity. A suitable dispenser must dispense appropriately sized particles at an appropriate velocity to penetrate the tissue covering the blood vessels within the buccal cavity, and must dispense a suitable volume to ensure that the portion actually reaching the buccal cavity represents the desired dose. Additionally, the device must not clog, which could prevent administering a dose when one is needed during a diabetic emergency. Furthermore, if insulin is the desired medication, the spray device must contain an insulin formulation adapted for buccal cavity delivery. Present metered dose inhalers typically dispense too little volume to ensure reliable buccal cavity delivery of a desired dose, and produce a fine aerosol mist of particles less than 5 microns in size, increasing the likelihood of inhalation of the medication into the lungs. The particles are not directed towards any specific portion of the mouth, but are placed generally inside the mouth where they may be inhaled or absorbed. Therefore, if the medication dispensed is insulin, use of a presently available metered dose spray device would result in possible side effects associated with lung delivery. Therefore, a metered dose spray device dispensing a sufficiently high quantity of medication, at a sufficiently high pressure, to ensure that a sufficient quantity will be propelled into the buccal cavity for proper absorption of the desired dose, is necessary.
Accordingly, an insulin formulation adapted for buccal cavity delivery is desired. Additionally, a metered dose spray device adapted for administering large-molecule medications such as insulin to the buccal region is desired.